1. Field of the Invention
The present invention relates to an internal combustion engine equipped with a plurality of combustion chambers such to allow the variation of the opening of the valves of said chambers by means of an actuator, specifically an internal combustion engine adapted for decompression braking.
2. Prior Art
Decompression braking systems in internal combustion engines are known, specifically in reciprocating engines such as the diesel engines used for heavy haulage. In these engines, decompression braking allows to reach very high specific braking powers, especially in concomitance with supercharging actuated by variable geometry turbo chargers.
It is known that such systems contemplate, during braking, a supplementary opening of the cylinder exhaust valve, to avoid the expansion of air in the cylinder after the compression stroke, which would reduce the braking efficacy.
Various types of devices are used to make such systems, including devices varying the fulcrum of a lever, which may be a rocker arm or a tappet, to allow it to be activated by parts of the camshaft cam profile normally not active due to the presence of higher movement clearance caused by such profile parts.
EP 0 543 210 requires the rockers arms to be fitted on eccentric bushings, in turn mounted on a rocker arm axle. A hydraulic actuator when required turns the bushing, thus displacing the rotation centre of the rocker arm.
Other systems contemplate different cams with different selectively activable levers, but these are very complex systems.
For reasons of construction simplicity and cost-effectiveness, it would be desirable to be able to use one single actuator for all cylinders. Furthermore, the positioning of the actuator is critical for the engine construction, and a suitable arrangement, also outside the engine cover would be preferable. This would also make the conditions, e.g. in relation to temperature and vibrations to which the actuator is subjected, less critical. Furthermore, the limitations of the dimensions of the actuator would be less stringent, with a suitable choice of location. This all would either make possible or facilitate the use of several types of actuators, for example pneumatic actuators.